Particle beam devices, for example electron beam devices, have been used for quite some time for examining objects (samples). Scanning electron microscopes (also referred to below as SEM) in particular are known.
An SEM has an electron beam column in which a beam generator and an objective lens are situated. With the aid of the beam generator, an electron beam is generated which is focused by the objective lens on an object to be examined. With the aid of a deflection device, the electron beam (also referred to below as a primary electron beam) is guided in a raster-like manner over the surface of the object to be examined. In the process, the electrons of the primary electron beam interact with the object. As a result of the interaction, in particular electrons are emitted from the object (so-called secondary electrons), or electrons of the primary electron beam are backscattered (so-called backscattered electrons). Secondary electrons and backscattered electrons form the so-called secondary beam, and are detected using a detector. The detector signal thus generated is used for image generation, for example.
Furthermore, it is known to additionally equip an SEM with an ion column (also referred to below as a combination device). With the aid of an ion beam generator situated in the ion column, ions are generated which are used for preparing objects (for example, ablating material from an object or applying material to an object), or also for imaging.
The previously described combination device is used, for example, for analyzing a crystal structure of an object. For this purpose, it is known from the prior art to determine the distribution of electrons which are backscattered at the object after incidence of a primary electron beam on the object. The above method is known as electron backscattering diffraction (EBSD). For example, to prepare for the method, a layer of a surface of an object to be analyzed is initially ablated with the aid of the ion beam. The primary electron beam is subsequently focused on an exposed layer of the surface of the object. Electrons are backscattered from the surface of the object due to the interaction of the electrons of the primary electron beam with the material of the object. The distribution of the backscattered electrons is determined in order to draw conclusions concerning the crystal structure of the object. Thus, information is basically obtained concerning the crystal structure with regard to this surface (i.e., in two dimensions).
To obtain information concerning the crystal structure in three dimensions, the exposed layer of the surface of the object to be analyzed is subsequently ablated, and then the primary electron beam is once again focused on an exposed layer of the surface of the object to be analyzed. Thus, an ablation of a layer of the object to be analyzed and an examination of a layer of the object to be analyzed which is exposed during the ablation are essentially carried out in alternation. By combining the information concerning the crystal structure of the individual surfaces, information concerning the crystal structure is then obtained in three dimensions (also referred to as 3D EBSD).
To determine the distribution of the backscattered electrons, a two-dimensional detector having a scintillator and a CCD camera, for example, is used.
For ablating the layer, it is known from the prior art to move the object to be analyzed into a first position, and for examining the exposed layer, to move the object to be analyzed into a second position. The motion occurs, for example, with the aid of an object holder on which the object to be analyzed is situated. The object holder has a design which, for example, is linearly movable in three mutually perpendicular directions. In addition, the object holder may, for example, be rotated about a first rotational axis and about a second rotational axis which is oriented perpendicularly to the first rotational axis. However, it is disadvantageous that each motion and/or rotation of the object holder is associated with an error due to mechanical factors. In other words, it is very likely that when a desired position of the object to be analyzed is adjusted, the object to be analyzed does not occupy this exact desired position. This results in errors in measuring the crystal structure of the object to be analyzed or requires time-consuming readjustment of the object holder.
To solve the above-described problem, a combination device is known from the prior art which is provided with a detector arrangement in such a way that the object no longer has to be moved in order to ablate a layer or to examine a layer. This known combination device has a first particle beam column, the first particle beam column having a first beam generator for generating a first particle beam, and a first objective lens for focusing the first particle beam on an object. The first particle beam column has a first beam axis. In addition, the combination device is provided with a second particle beam column, the second particle beam column having a second beam generator for generating a second particle beam, and a second objective lens for focusing the second particle beam on the object. In addition, the second particle beam column has a second beam axis. The first beam axis of the first particle beam column and the second beam axis of the second particle beam column define a first angle of approximately 50° to approximately 60°. In addition, the first beam axis of the first particle beam column and the second beam axis of the second particle beam column are situated in a first plane. Furthermore, the combination device is provided with a detector for detecting electrons which are backscattered from the object and which are used for carrying out the EBSD method. A detection axis which is situated in a second plane extends from the detector to the object. The first beam axis is likewise situated in the second plane. The first plane and the second plane define a second angle which is exactly 90°.
However, it has been shown that the measuring results which are obtained from the EBSD method carried out using the above-mentioned combination device are not satisfactory enough to identify the crystal structure of an object to be analyzed with acceptable quality. In addition, it has turned out that processing an object with the aid of a particle beam does not provide sufficiently good results. Furthermore, for the known combination device it is not possible to process the object with the aid of a first particle beam and simultaneously carry out the above-described EBSD method with the aid of a second particle beam.
Accordingly, it would be desirable to provide a particle beam device using which a method may be carried out so that in particular crystal structures of objects to be analyzed are satisfactorily identified. In addition, it should not be absolutely necessary to move an object between a processing position and an analyzing position in which the EBSD method is carried out. Furthermore, it is desirable for an object to be processable with the aid of a particle beam with grazing incidence of the particle beam on the object. The phrase “with grazing incidence” is understood to mean that the angle between the particle beam axis and the surface to be processed is small, for example, less than 4°.